1. Field of the Invention
The present invention relates to diffusers and, more particularly, to air diffusers for treating wastewater in wastewater treatment plants.
2. Description of the Prior Art
In wastewater treatment plants, it is known to aerate effluent, or sludge, as part of the wastewater purification process. This process is commonly known as the xe2x80x9cactivatedxe2x80x9d sludge process. In the activated sludge process, air is introduced near the bottom of an aeration tank containing wastewater and bacterial floc via a system of pipes and/or hoses. As the air rises to the surface as air bubbles, some of the oxygen in the air is transferred to the wastewater and is consumed by the bacteria during digestion which aids in the treatment of sewage. One prior art sludge aeration tank utilizes rubber check valves or the like to provide air to the wastewater. It is also known to use air diffusers in the shape of a dome in the activated sludge process. These air diffusers are typically made of porous ceramic or plastic.
There are several common problems with domed air diffusers (hereinafter xe2x80x9cair diffusersxe2x80x9d) which are currently used in the activated sludge process. For example, some current state-of-the-art air diffusers cannot prevent the backflow of sludge and algae into the air supply source. To overcome this disadvantage, the air supply source must run continuously to prevent the backflow of sludge into the air supply source. As a result, energy consumption of the air supply source, typically an air compressor, is usually the single most expensive cost in the operation of wastewater treatment plants. In the event the air supply to the air diffuser is shut off, sludge, organic matter and other debris will back into the air supply source and foul the air compressor and its controls.
In addition, prior art air diffusers easily become plugged with accumulated algae and sludge that settles on and within the air diffuser during the activated sludge process. Consequently, it would be beneficial to provide an air diffuser which overcomes these disadvantages in the prior art.
It is therefore an object of the present invention to provide an air diffuser that can prevent backflow into the air diffuser""s air supply source, without the need to continuously run air through the air diffuser.
It is a further object of the present invention to provide an air diffuser capable of providing aeration to sludge in wastewater treatment plants without becoming easily plugged with organic material.
The above objects are satisfied with a diffuser for diffusing a process fluid made in accordance with the present invention. The diffuser generally includes a base member having a first side and a second side, with the base member having an inlet conduit depending from the second side. The inlet conduit defines a central bore extending through the base member. A resilient dome member is sealed to the first side of the base member at a peripheral edge of the first side of the base member. The dome member defines a plurality of perforated holes extending therethrough. A coupling member is at least partially positioned within the central bore and configured to cooperate with an external process fluid source.
In a pressurized state of the diffuser, the process fluid flows through the central bore and expands the dome member such that a cavity forms between an inner surface of the dome member and the first side of the base member. In addition, in the pressurized state of the diffuser, the process fluid diffuses from the diffuser through the perforated holes in the dome member.
The dome member and the coupling member may be integrally formed as part of the base member. The dome member may include at least one elastomer ply, with a plurality of perforated holes defined therethrough. The dome member may further include a nonperforated area opposite the central bore. In an unpressurized state of the diffuser, the nonperforated area may contact the first side of the base member and may seal the central bore from backflow therethrough.
The coupling member may be a check valve. The base member may be made of a high durometer rubber of about 90 Shore A, and the dome member may be made of a low durometer rubber of about 45 Shore A. A distribution of the plurality of perforated holes in the dome member is preferably about 32 holes/inch2. In the pressurized state of the diffuser, the cavity may have a semicircular-shaped or polygonal-shaped cross section.
In a second embodiment of the present invention, the diffuser includes a base member having a first side and a second side. The base member defines a longitudinally extending inlet having an inlet opening. A resilient dome member is sealed to the first side of the base member at a peripheral edge of the first side such that a first portion of the dome member encloses the inlet conduit and the inlet opening. A second portion of the dome member defines a plurality of perforated holes extending therethrough. A coupling member is at least partially positioned within the inlet conduit and configured to cooperate with an external process fluid source.
In a pressurized state of the diffuser, the process fluid flows through the inlet conduit such that the dome member expands and forms a cavity between an inner surface of the dome member and the first side of the base member. In addition, in the pressurized state of the diffuser, the process fluid diffuses through the perforated holes defined in the second portion of the dome member. In an unpressurized state of the diffuser, the first portion of the dome member contacts the first side of the base member and seals the inlet opening from backflow.
The first portion of the dome member may further include a nonperforated area opposite the inlet opening of the inlet conduit. In an unpressurized state of the diffuser, the nonperforated area may contact the first side of the base member and may seal the inlet opening from backflow therethrough. In addition, the diffuser, in this embodiment, may include a longitudinally extending flop zone formed by the base member and the dome member immediately adjacent the inlet opening of the inlet conduit. The present invention also includes a method of using a diffuser to diffuse a process fluid.
Further details and advantages of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawings, wherein like parts in succeeding embodiments are designated with primed reference numerals.